A great writeup and a really nice set of improvements to this otherwise pretty basic device.
That said, it absolutely boggles the mind that an HDMI output for this thing would be taken care of by an RPi, that is many orders of magnitude more powerful, and power efficient than the device at hand.
We've got 3x spectrums, two 48k rubber key ones and a plus2. we've even got such random things as a Trickstick :)(https://worldofspectrum.org/hardware/feat4.html). I got them out of the loft the other day but the biggest problem i found is that few of the original game tapes still work. did manage to play Jetpac though :)
I have kept my Spectrum 48k and QL stored in reasonable condition but have not booted them in decades. Probably will need some work if I ever get round to them.
Don't just plug them in randomly! The original power brick can get out of spec (delivering over-voltage), and the voltage regulator on the PCB commonly fails. In the worst case this can end up permanently damaging other components. There's a routine you can follow to test each part, although you'll need a multimeter and some experience, and a bench power supply will come in handy as well.
Yes, do. Although I have one whose output seems OK but doesn't power the system ok when connected. They definitely were built to be cheap rather than to an engineering standard!
Not slating them, times were different and every penny counted. I've got 4 spectrums here... 3 are 48k but one is original 16k....which is the most interesting one but it's the one that doesn't work!
I have one of these, sitting in a box since I bought it for peanuts many years ago (sold as a 48K).
I like it but, due to lack of time and expertise to take care of it, I have been debating whether to keep or donate all my old machines the local ZX Spectrum museum a short drive away from me. Certainly a brighter future than a box somewhere...
7805's are linear regulators, they drop excess voltage as heat. Using a 2A rated 7805 won't make it run less hot, the heat output is the delta between input and output voltages.
Not necessarily, the higher rated packages are rated higher because they use higher quality materials that have a lower thermal coefficient (for getting the heat out), so yes the energy in Watts is the same but they’ll still probably run cooler.
If you’re interested whether this is the case you’d look for a thing called “junction thermal coefficient” on the data sheet.
It's been ~15 years since I did much with 78xx's, but I seem to recall the various package types were all pretty much the same on thermal coefficients, and other related specs. It's a decades-old design that has been pretty well optimized at this point. The 2A versions also have slightly bigger leads, which may not fit in through-holes not sized for them originally.
Are there not 7805 replacements which internally are switch mode? (It seems almost miraculous to me that we could miniaturise a switch mode power supply into such a tiny device.)
There’s something incredibly satisfying about breathing life back into vintage machines. The Toastrack was my first intro to BASIC as a kid — amazing how much those 8-bits taught us.
I still have mine, although it was my 2nd Spectrum.
I am still sad and annoyed that Sinclair Research took the technologically very conservative design from Investronica in Spain, and not the older, existing, and more ambitious design from Timex in the USA for the Timex-Sinclair 2068.
The Investronica 128 had an industry-standard sound chip, and used its I/O ports for some fairly pointless extras, like MIDI, RS232 and a numeric keypad. I have a keypad for mine, but nobody cared. It also had extra RAM and that's about it.
The American machine had the same sound chip, a ROM cartridge slot, 2 joystick ports (so, equivalent to a built-in Sinclair Interface 2), and also 2 better graphics modes, and could page out the ROM for CP/M. The same paging mechanism allowed more RAM just like the Spanish machine.
The joystick ports were far more worthwhile than a numeric keypad or a serial port.
Amstrad later copied the joystick ports, and later still CP/M, but nothing else.
Absolutely. I have lots of fun restoring old machines; it's one of my favourite hobbies. Not only do I get a nostalgia kick from remembering systems from my younger years, but I also learn a great deal about how they worked internally and about electronics. Once they're fixed, I lose interest and move to the next project.
The later Spectrum's were some of the nicest looking 8 bit machines... As a Commodore (VIC 20, C64, Amiga) user, it was the one thing I liked about them...
The later real Sinclair ones like the QL. Rick Dickinson, who did these designs, was responsible for designing the recent Kickstarted ZX Spectrum Next, which is a lovely machine.
A great writeup and a really nice set of improvements to this otherwise pretty basic device.
That said, it absolutely boggles the mind that an HDMI output for this thing would be taken care of by an RPi, that is many orders of magnitude more powerful, and power efficient than the device at hand.
> it absolutely boggles the mind that an HDMI output for this thing would be taken care of by an RPi
There's a much much easier way:
https://www.bytedelight.com/?product_cat=videoaudio
The HDMI licence costs quite a lot. It's much cheaper for small runs to use a device with one onboard, and let it emit the very expensive signals.
We've got 3x spectrums, two 48k rubber key ones and a plus2. we've even got such random things as a Trickstick :)(https://worldofspectrum.org/hardware/feat4.html). I got them out of the loft the other day but the biggest problem i found is that few of the original game tapes still work. did manage to play Jetpac though :)
I have kept my Spectrum 48k and QL stored in reasonable condition but have not booted them in decades. Probably will need some work if I ever get round to them.
Don't just plug them in randomly! The original power brick can get out of spec (delivering over-voltage), and the voltage regulator on the PCB commonly fails. In the worst case this can end up permanently damaging other components. There's a routine you can follow to test each part, although you'll need a multimeter and some experience, and a bench power supply will come in handy as well.
I'd recommend looking at these sites: https://retrorepairsandrefurbs.com/sinclair-computers/ https://www.retroleum.co.uk/
and Lee on Youtube: https://www.youtube.com/@MoreFunMakingIt/videos https://www.youtube.com/@morefunfixingit/videos plus Lee has a Discord where they discuss fixing old Sinclairs, linked here: https://www.morefunmakingit.co.uk/links/.
Thx for the advice. Will definitely measure the power bricks before plugging them in.
Yes, do. Although I have one whose output seems OK but doesn't power the system ok when connected. They definitely were built to be cheap rather than to an engineering standard!
Not slating them, times were different and every penny counted. I've got 4 spectrums here... 3 are 48k but one is original 16k....which is the most interesting one but it's the one that doesn't work!
A modern Meanwell power supply is simply going to be safer as well as far more efficient (and smaller!) Just make sure you get the polarity right.
This stackexchange question is quite good on how and why the 9VDC supply at the jack gets converted to 5V, 12V and -5V internally: https://retrocomputing.stackexchange.com/questions/2242/how-...
I have one of these, sitting in a box since I bought it for peanuts many years ago (sold as a 48K).
I like it but, due to lack of time and expertise to take care of it, I have been debating whether to keep or donate all my old machines the local ZX Spectrum museum a short drive away from me. Certainly a brighter future than a box somewhere...
This one? https://loadzx.com/en/
If yes, they will be in very good hands.
yes, this one!
Donate it. What use is it sitting in storage forever, unused?
7805's are linear regulators, they drop excess voltage as heat. Using a 2A rated 7805 won't make it run less hot, the heat output is the delta between input and output voltages.
Not necessarily, the higher rated packages are rated higher because they use higher quality materials that have a lower thermal coefficient (for getting the heat out), so yes the energy in Watts is the same but they’ll still probably run cooler.
If you’re interested whether this is the case you’d look for a thing called “junction thermal coefficient” on the data sheet.
It's been ~15 years since I did much with 78xx's, but I seem to recall the various package types were all pretty much the same on thermal coefficients, and other related specs. It's a decades-old design that has been pretty well optimized at this point. The 2A versions also have slightly bigger leads, which may not fit in through-holes not sized for them originally.
Are there not 7805 replacements which internally are switch mode? (It seems almost miraculous to me that we could miniaturise a switch mode power supply into such a tiny device.)
Edit: I was thinking of: https://www.adafruit.com/product/1065
Those are great little things. There are many options from a bunch of different manufacturers: https://www.digikey.com/short/44v55n0r
Yep, but: 2A 7805 are less likely to get damaged for the heat. The failure rate of the 7805 can be observed especially in the Commodore 64 PSUs.
Good point. I should know this.
There’s something incredibly satisfying about breathing life back into vintage machines. The Toastrack was my first intro to BASIC as a kid — amazing how much those 8-bits taught us.
I still have mine, although it was my 2nd Spectrum.
I am still sad and annoyed that Sinclair Research took the technologically very conservative design from Investronica in Spain, and not the older, existing, and more ambitious design from Timex in the USA for the Timex-Sinclair 2068.
The Investronica 128 had an industry-standard sound chip, and used its I/O ports for some fairly pointless extras, like MIDI, RS232 and a numeric keypad. I have a keypad for mine, but nobody cared. It also had extra RAM and that's about it.
The American machine had the same sound chip, a ROM cartridge slot, 2 joystick ports (so, equivalent to a built-in Sinclair Interface 2), and also 2 better graphics modes, and could page out the ROM for CP/M. The same paging mechanism allowed more RAM just like the Spanish machine.
The joystick ports were far more worthwhile than a numeric keypad or a serial port.
Amstrad later copied the joystick ports, and later still CP/M, but nothing else.
Absolutely. I have lots of fun restoring old machines; it's one of my favourite hobbies. Not only do I get a nostalgia kick from remembering systems from my younger years, but I also learn a great deal about how they worked internally and about electronics. Once they're fixed, I lose interest and move to the next project.
The later Spectrum's were some of the nicest looking 8 bit machines... As a Commodore (VIC 20, C64, Amiga) user, it was the one thing I liked about them...
The later real Sinclair ones like the QL. Rick Dickinson, who did these designs, was responsible for designing the recent Kickstarted ZX Spectrum Next, which is a lovely machine.
<3 Triudos <3
The shop window of wonder ;)
:) Centro Comercial Fonte Nova em Lisboa.
Exactamente aí estava essa montra :)